Is there an asset for that ? Need advice on game mechanics / game logic

Still working on my very first game (a basic 2D Platformer); i'm confronted with the following issue I don't know how to implement the leveling up of the player; let me explain:

The player kills ennemies and collect coins; those coins give the player experience; each 100 experience points the player levels up (quite dumb, yay).

Here's the catch:

When the player is in Level1, i only want to generate some kind of enemies, and only some kind of power ups ; ideally i would like to put everything in a 'List' in a game object that would check where the player is, and if it matches then only generated that kind of ennemies and powerups.

In level 2, i'd have new kind of enemies and new power ups etc ...

I want this to be 'easy' to do, like just drop in the editor and voilà; but my skills in editorGUI stuff is quite limited for now.

I've been trying to figure out a way to do this, but since this is kind of 'basic' i was wondering what was the proper way of doing.

If somebody could point me to a starting point that would be fantastic.

Thanks